1. Field of the Invention
The present invention relates to a method of producing amides and amides containing a hetero ring in their molecules which are useful as photographic couplers, photographic additives, medicines and agricultural chemicals or synthetic intermediates of these compounds.
2. Description of the Related Art
Amides and amides containing a hetero ring in their molecules are useful as photographic couplers, photographic additives, medicines and agricultural chemicals or synthetic intermediates of these compounds. Methods of producing these amides have been studied actively so far.
Generally, amides are produced from corresponding carboxylic acids or esters. Examples of methods of producing amides from esters among these starting materials include (1) a method in which esters are first hydrolyzed into carboxylic acids, which are then converted into acid halides, followed by reacting these acid halides with amines (2) and a method in which esters are condensed directly with amines in the presence of a catalyst. There are many unsatisfactory aspects as an industrial production method in the method (1), such as that the method (1) involves many steps and requires anticorrosive production apparatus. On the other hand, the method (2) is carried out in the presence of a protonic acid or Lewis acid catalyst. Examples of Lewis acids which have been hitherto known include tin compounds (e.g., Japanese Patent Application Laid-Open (JP-A) Nos. 62-67055, 54-138513 and 2000-95741), compounds of elements of group III in the periodic table (e.g., JP-A Nos. 2001-261625 and 9-239270), titanium, iron or zinc compounds (e.g., JP-A No. 8-134041) and indium compounds (for example, “Synthetic Communications”, vol. 33, p. 297 (2003)). Also, aluminum chloride and aluminum bromide may be used as the Lewis acid, as disclosed in, for example, “Synthetic Communications”, vol. 16, 633 (1986).
The production methods using a protonic acid or these catalysts are unsatisfactory as industrial production methods from the standpoints of low yields and the generation of many byproducts, and solution of these problems has been demanded.